Method for controlling electric compressor

ABSTRACT

Disclosed is a method of controlling an electric compressor. The method includes: (I) starting the electric compressor by applying an electric power to an air conditioner; (II) determining, by an inverter, whether the electric compressor is started normally; and normally driving the electric compressor when the electric compressor starts normally in the step (II) and determining again whether the electric compressor starts normally by restarting the electric compressor. Therefore, abnormal operation such as malfunction, short, and overheating of the electric compressor is detected in the early starting stage to determine restarting and failure of starting the electric compressor so that reliability of the electric compressor may be enhanced.

TECHNICAL FIELD

The present invention relates to a method of controlling an electric compressor, and more particularly to a method of controlling an electric compressor such that abnormal operations of the electric compressor such as malfunction, short, and overheating are promptly detected by an inverter at early starting time of the compressor to determine restarting of the electric compressor or failure of starting of the electric compressor resulting in improvement of reliability of the electric compressor.

BACKGROUND ART

In general, compressors applied to air conditioning systems are divided into various types such as a reciprocating compressor, a rotary compressor, and a scroll compressor according to the operating types.

Furthermore, an electric compressor employing an electric motor as a driving source includes a motor unit having a driving motor and a compressor unit for compressing refrigerant.

In general, the electric compressor includes an inverter installed at a side of a compressor housing to control revolutions per minute of the driving motor for the variable control of air conditioning efficiency of an air conditioning system when an external load varies.

In more detail, the inverter includes a printed circuit board (PCB) on which various circuit elements are mounted and is disposed in an inverter housing provided at a side of the compressor housing while being insulated by a cover for covering an opening of the inverter housing.

However, the conventional electric compressor guarantees stability by switching on/off a clutch at abnormal operation such as malfunction, short, and overheating.

That is, in connection with the conventional electric compressor, there is none of technology of detecting abnormal operation of the electric compressor at the early start by the inverter to determine whether to start the electric compressor again or failure of start of the electric compressor.

Moreover, the conventional inverters are classified into a sensor type inverter of controlling speed of a driving motor by monitoring position of a rotor using a position sensor such as a hall sensor, and a sensorless inverter of controlling speed of a driving motor by estimating position of the rotor based on counter electromotive force or current of the driving motor without a position sensor. In recent, the sensorless inverter is preferred.

However, the conventional sensorless inverter has difficulty in detecting abnormal operation of a device of the inverter, short between a motor and the inverter, and malfunction of the motor early so that reliable operation may be deteriorated.

DISCLOSURE OF INVENTION

It is, therefore, an object of the present invention to provide a method of controlling an electric compressor such that abnormal operations of the electric compressor such as malfunction, short, and overheating are promptly detected by an inverter at early starting time of the compressor to determine restarting of the electric compressor or failure of starting of the electric compressor resulting in improvement of reliability of the electric compressor.

It is another object of the present invention to provide a method of controlling an electric compressor by detecting abnormal operation of an inverter and malfunction and short of a motor before starting of the electric compressor so that reliability may be enhanced.

In accordance with an aspect of the present invention, there is provided a method of controlling an electric compressor including: (I) starting the electric compressor by applying an electric power to an air conditioner; (II) determining, by an inverter, whether the electric compressor is started normally; and (III) normally driving the electric compressor when the electric compressor starts normally in the step (II) and determining again whether the electric compressor starts normally by restarting the electric compressor when the electric compressor does not start normally.

Preferably, after the step (III), the electric compressor is driven normally when the electric compressor starts normally and the step (III) is repeated by a preset times when the electric compressor does not start normally.

Preferably, when the electric compressor does not starts normally even after repeating the step (III) by the preset times, failure of starting of the electric compressor is determined and an error message is outputted.

Preferably, a preset standby time for restarting of the electric compressor is provided when the step (III) is repeated.

Preferably, moreover, a starting current when the step (III) is repeated is within Max ±25% of a driving current.

In accordance with another aspect of the present invention, there is provided an electric compressor controlling method of detecting abnormal operation of an inverter or a driving motor before starting the electric compressor, including: (I) applying an electric power to an air conditioner; (II) detecting currents of three phases by a sensor by applying a minute current to the driving motor of the electric compressor; and (III) determining the abnormal operation of the inverter or the driving motor using sum of the three phase currents (Ui+Vi+Wi).

Preferably, the electric compressor is normally started or driven when the sum of the three phase currents is 0 (zero) or within an error range and it is determined that the inverter or the driving motor is malfunctioned and an error message is outputted when the sum of the three phase currents is not 0 (zero) or out of the error range.

Preferably, the step (III) is carried out within 1 (one) second.

Preferably, the sensor may be a current sensor or a resistive sensor.

In accordance with still another aspect of the present invention, there is provided an electric compressor controlling method of detecting abnormal operation of an inverter or a driving motor of an electric compressor before starting the electric compressor, including: (I) applying an electric power to an air conditioner; (II) detecting two of three phase currents (Ui, Vi, and Wi) by a sensor by applying a minute current to the driving motor of the electric compressor; (III) calculating remaining one phase current from the two phase currents; and (IV) determining whether the inverter or the driving motor is operated abnormally by comparing the three phase currents (Ui, Vi, and Wi) with a reference current.

Preferably, in the step (III), the remaining one phase current is obtained from the two phase currents from the fact that sum of the three phase currents (Ui+Vi+Wi) is 0 (zero).

Preferably, after the step (IV), the electric compressor is normally started or driven when the three phase currents (Ui+Vi+Wi) are within an error range of the reference current and the inverter or the driving motor is determined as being malfunctioned and an error message is outputted when the three phase currents (Ui+Vi+Wi) are out of the error range of the reference current.

Preferably, the step (IV) is carried out within 1 (one) second.

Preferably, the sensor may be a current sensor or a resistive sensor.

EFFECT OF THE INVENTION

According to the method of controlling an electric compressor in accordance with the present invention, abnormal operations such as malfunction, short, and overheating of the electric compressor can be detected by an inverter at the early starting time of the electric compressor to determine restarting of the electric compressor or failure of starting the electric compressor so that reliability of the electric compressor may be enhanced.

Moreover, three phase currents of the driving motor are measured by a sensor before starting the electric compressor such that abnormal operation of the inverter and malfunction or short of the motor can be determined promptly.

In other words, stable operation of the inverter may be achieved and troubleshooting of the driving motor can be detected in early stage so that accident may be prevented.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a sectional view schematically illustrating an electric compressor used in the present invention;

FIG. 2 is a flowchart illustrating a method of controlling an electric compressor according to an exemplary embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method controlling an electric compressor according to another exemplary embodiment of the present invention; and

FIG. 4 is a flowchart illustrating a method controlling an electric compressor according to still another exemplary embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view schematically illustrating an electric compressor used in the present invention. FIG. 2 is a flowchart illustrating a method of controlling an electric compressor according to an exemplary embodiment of the present invention.

FIG. 3 is a flowchart illustrating a method controlling an electric compressor according to another exemplary embodiment of the present invention.

FIG. 4 is a flowchart illustrating a method controlling an electric compressor according to still another exemplary embodiment of the present invention.

Before description of the method of controlling an electric compressor according to an exemplary embodiment of the present invention, an electric compressor will be described for better understanding of the present invention.

As illustrated in FIG. 1, an inverter 100 is mounted at a side of an electric compressor according to an exemplary embodiment.

The electric compressor is an element of an air conditioner and has a driving shaft rotated not by a driving force transmitted from a power generating device such as an engine but by a driving motor mounted in a compressor housing.

That is, the electric compressor includes a compressor unit 200 provided with devices for compressing refrigerant therein and a driving unit 300 having a driving motor for driving the compressor unit. The inverter 100 is installed in an inverter housing 500 which is provided at an outer circumference of the compressor housing, near a side where the driving motor is disposed, specifically on a side of the outer circumference, and an upper opening of which is covered by a cover 400.

In this case, the inverter 100 performs variable control of revolutions per minute (RPM) of the driving motor to adjust flow rate of refrigerant circulating by the refrigerating cycle of an air conditioner and is electrically connected to the driving motor by a terminal or a bus bar.

The inverter 100 includes a printed circuit board (PCB) on which various circuit devices such as an MCU having an IC on which an inverter operating program is stored, an intelligent power module (IPM) on which an insulated gate bipolar transistor (IGBT) or a motor drive function is loaded, a regulator, an inductor, a capacitor, etc., are mounted.

The inverter 100 has a function of determining failure of starting an electric compressor to enhance reliability of the electric compressor.

In addition, the inverter 100 may be a sensorless inverter estimating position of a rotor based on counter electromotive force and current of the driving motor without a position sensor to control RPM of the driving motor.

The sensorless inverter includes sensors detecting position of the rotor before starting of the compressor wherein the sensor are installed to three phases U, V, and W of the three phase driving motor to measure currents. Here, the sensors may be current sensors or resistive sensors.

Thus, the sensors measure currents of three phases such that abnormal operation of the inverter and malfunction or short of the motor are determined at early stage so that reliability may be enhanced.

Hereinafter, the method of controlling an electric compressor will be described in detail with reference to the accompanying drawings.

Exemplary Embodiment 1

As illustrated in FIG. 2, according to a method of controlling an electric compressor according to an exemplary embodiment of the present invention to determine whether the electric compressor is failed to start, an electric power is applied to a temperature controller such as an FATC (S110).

Next, revolutions of the driving motor are assigned to start the electric compressor (S120 and S130).

Then, the inverter determines whether the electric compressor starts normally (S140).

That is, the inverter determines whether there is abnormal operation of the compressor such as malfunction, short, and overheating at the early start of the electric compressor. The electric compressor is driven normally when the electric compressor is started normally (S150) while the following step (S160) is carried out when the electric compressor is not started normally.

Next, the electric compressor is restarted to determine whether the electric compressor is started (S160).

That is, the electric compressor is driven normally when the electric compressor is started normally (S150) or the step (S160) is repeated by a preset times when the electric compressor is not started normally (S170 and S180).

In this case, the repetition times may be 5 (five).

Meanwhile, when the step of restarting the electric compressor (S160) is repeated, there is a standby time (S190).

The stable starting of the electric compressor is enabled by stand by until pressure difference between intake and discharge is reduced, wherein the standby time may range from 0 (zero) to 5 (five) seconds.

Moreover, the starting current in the step of restarting the electric compressor (S160) maintains Max ±25% of drive current (S200).

When the electric compressor is not started normally even after the step (S160) is repeated by the preset times, this case is determined failure of starting the electric compressor, an error message is output, and all processes are ended (S210 and S220).

Exemplary Embodiment 2

As illustrated in FIG. 3, according to a method of controlling an electric compressor according to this exemplary embodiment of the present invention to determine abnormal operation of an inverter and malfunction and short of a motor, an electric power is applied to an air conditioner (S210).

Next, a minute current is applied to a driving motor of the electric compressor to measure currents of three phases Ui, Vi, and Wi (S220).

With the three phase currents Ui, Vi, and Wi measured in step 5220, whether the inverter and the driving motor are abnormal is determined (S230).

In this case, the inverter or the driving motor is determined normal such that the electric compressor is started normally when sum of the three phase currents Ui+Vi+Wi is 0 (zero) or within an error range (S240). Otherwise, when the sum of three phase currents Ui+Vi+Wi is out of the error range, the inverter or the driving motor is determined to be malfunctioned (S250).

Specifically, in a three phase driving motor, the sum of three phase current is 0 (zero) as expressed by the following equation 1.

Thus, when wrong measured currents Ui, Vi, and Wi are provided by abnormal operation of the inverter and malfunction or short of the motor, the sum of the wrong measured currents cannot be 0 (zero) so that the inverter or the driving motor is determined as being malfunctioned.

Meanwhile, the step S230 may be carried out within 1 (one) second such that responsibility of starting of a compressor may be improved.

[Equation 1]

U _(i) +V _(i) +W=0

Next, after the step S250, an error message is outputted to stop the electric compressor (S160).

Exemplary Embodiment 3

As illustrated in FIG. 4, according to a method of controlling an electric compressor according to this exemplary embodiment of the present invention to determine abnormal operation of an inverter and malfunction and short of a motor, an electric power is applied to an air conditioner (S310).

Next, a minute current is applied to a driving motor of the electric compressor to measure two of the three phase currents Ui, Vi, and Wi (S320).

The remaining one phase current is calculated from the measured two phase currents (S330).

In this case, since sum of the three phase currents Ui+Vi+Wi is 0 (zero) as expressed by equation 1, the remaining one phase current is calculated.

Each of the three phase currents Ui, Vi, and Wi is compared with a reference current to determine abnormal operation of the inverter and the driving motor (S340).

In this case, when each of the three phase currents Ui, Vi, and Wi is within an error range of the reference current, the electric compressor is started normally (S350). Otherwise, when the three phase currents Ui, Vi, and Wi are out of the error range of the reference current, the inverter or the driving motor is determined as being malfunctioned (S360).

In specifically, the reference current is currents of the three phases measured at the normal starting of the electric compressor. Thus, when the three phase currents Ui, Vi, and Wi measured and calculated in the step are out of the error range of the reference current, the inverter or the driving motor is determined as being malfunctioned.

Meanwhile, the step S340 may be carried out within 1 (one) second so that reliability of the electric compressor may be improved.

After step S360, an error message is outputted to stop the electric compressor (S370).

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 

1. A method of controlling an electric compressor comprising: (I) starting the electric compressor by applying an electric power to an air conditioner; (II) determining, by an inverter, whether the electric compressor is started normally; and (III) normally driving the electric compressor when the electric compressor starts normally in the step (II) and determining again whether the electric compressor starts normally by restarting the electric compressor when the electric compressor does not start normally.
 2. The method of claim 1, wherein, after the step (III), the electric compressor is driven normally when the electric compressor starts normally and the step (III) is repeated by a preset times when the electric compressor does not start normally.
 3. The method of claim 2, wherein, when the electric compressor does not starts normally even after repeating the step (III) by the preset times, failure of starting of the electric compressor is determined and an error message is outputted.
 4. The method of claim 2, wherein a preset stand-by time for restarting of the electric compressor is provided when the step (III) is repeated.
 5. The method of claim 2, wherein a starting current when the step (III) is repeated is within Max ±25% of a driving current.
 6. An electric compressor controlling method of detecting abnormal operation of an inverter or a driving motor before starting the electric compressor, comprising: (I) applying an electric power to an air conditioner; (II) detecting currents of three phases by a sensor by applying a minute current to the driving motor of the electric compressor; and (III) determining the abnormal operation of the inverter or the driving motor using sum of the three phase currents (Ui+Vi+Wi).
 7. The electric compressor controlling method of claim 6, wherein the electric compressor is normally started or driven when the sum of the three phase currents is 0 (zero) or within an error range and it is determined that the inverter or the driving motor is malfunctioned and an error message is outputted when the sum of the three phase currents is not 0 (zero) or out of the error range.
 8. The electric compressor controlling method of claim 6, wherein the step (III) is carried out within 1 (one) second.
 9. The electric compressor controlling method of claim 8, wherein the sensor comprises a current sensor or a resistive sensor.
 10. An electric compressor controlling method of detecting abnormal operation of an inverter or a driving motor of an electric compressor before starting the electric compressor, comprising: (I) applying an electric power to an air conditioner; (II) detecting two of three phase currents (Ui, Vi, and Wi) by a sensor by applying a minute current to the driving motor of the electric compressor; (III) calculating remaining one phase current from the two phase currents; and (IV) determining whether the inverter or the driving motor is operated abnormally by comparing the three phase currents (Ui, Vi, and Wi) with a reference current.
 11. The electric compressor controlling method of claim 10, wherein, in the step (III), the remaining one phase current is obtained from the two phase currents from the fact that sum of the three phase currents (Ui+Vi+Wi) is 0 (zero).
 12. The electric compressor controlling method of claim 11, wherein, after the step (IV), the electric compressor is normally started or driven when the three phase currents (Ui+Vi+Wi) are within an error range of the reference current and the inverter or the driving motor is determined as being malfunctioned and an error message is outputted when the three phase currents (Ui+Vi+Wi) are out of the error range of the reference current.
 13. The electric compressor controlling method of claim 10, wherein the step (IV) is carried out within 1 (one) second.
 14. The electric compressor controlling method of claim 13, wherein the sensor comprises a current sensor or a resistive sensor. 